Glass fiber mats are composed of glass fibers held together by a binder material. Typical binders used in the industry are urea-formaldehyde resins, phenolic resins, polyvinyl alcohols, and latexes. These binder materials are coated directly on the fibers of the mat and set or cured to provide the desired integrity for the glass fibers. The most widely used binder is urea-formaldehyde because it is inexpensive. Unfortunately, urea-formaldehyde binder is deficient in one or more respects for glass fiber mats. In particular, the tensile strengths of mats bound with urea-formaldehyde may deteriorate appreciably when the mats are subjected to wet conditions, such as normally encountered by incorporating such mats in roofing products. Such products may fail if wet tensile strength is much lower than dry tensile strength.
U.S. Pat. No. 4,430,158 teaches the addition of certain anionic surfactants to urea-formaldehyde binder as a means of improving wet tensile strength of glass fiber mats.
U.S. Pat. No. 4,178,203 to Chakrabarti teaches addition of surfactants to newly formed wet glass mat to improve the wet strength of the newly formed mat so that it does not fall apart while being transferred to subsequent operations such as application of binder. The Chakrabarti process does not result in any significant improvement in the tensile strength of the finished mat.
It is an object of this invention to provide glass fiber mat of improved tensile strength for use in manufacturing products such as roofing shingles and built-up roofing products.